Further tests of cast C4 blades in the vortex wind tunnel.

Extensive tests on the Vortex Wind Tunnel fitted with sand cast blades of free vortex design, have been carried out. The performance of the blades is much better than obtained in previous tests (Ref. 3) and this is attributed to modifications made to the tunnel. Whenever possible, the results from the tests are compared with two dimensional cascade data (Refs. 4, 6 and 15), and radial equilibrium studies are made on the flow. The agreement between the actual blade performance and the cascade data, is good, considering that the blades themselves are not of design shape. The flow appears to have almost reached a state of radial equilibrium-i chord lengths downstream of the blade rows. By examining data on secondary flows, (Ref. 10, 11, 16 and 17), and results from the Vortex Wind Tunnel, a picture of secondary flow formation is presented.